It is a polite way to ask someone if they would like something, and it is often used when offering something to someone.
Here are some examples:
* "¿Te gustaría un café?" - "Would you like a coffee?"
* "¿Te gustaría ir al cine?" - "Would you like to go to the cinema?"
* "¿Te gustaría un poco de chocolate?" - "Would you like some chocolate?"